A major problem in developmental biology is to determine when and how time and position-restricted instructions are signalled and received during secondary embryonic inductions such as branching morphogenesis. Morphogenesis of embryonic mouse lungs cultured in vitro under serumless, chemically defined conditions is similar to lung development in vivo: branching morphogenesis and cytodifferentiation of type II pneumocytes occurs, suggesting the hypothesis that endogenous growth factors serve as instructive epigenetic signals. We hypothesize that EGF and TGF-alpha serve as local autocrine and paracrine epigenetic signals to regulate the three-dimensional timing and positional information for epithelial branching during lung morphogenesis in the mouse embryo and that these signals are transduced via activation of the EGF receptor. The Specific Aims of this project are designed to test this hypothesis: Aim 1. Localization: to detect and localize in time and space expression of EGF and TGF-alpha at the mRNA and protein levels during branching morphogenesis in embryonic (E. 11/12) mouse lung both in vivo and in culture in chemically-defined serum free medium. Aim 2. Signal transduction: to characterize and localize EGF receptor tyrosine phosphorylation signal transduction pathway. Aim 3. Inhibitory strategies: to investigate the developmental effects of EGF receptor activation during lung morphogenesis in vitro using inhibitory strategies with tyrphostins, antibodies, or antisense cRNA probes. Future goals of this research include identification of specific genes regulated by EGF receptor activation during mouse lung morphogenesis in vitro. The proposed studies will characterize novel EGF receptor mediated autocrine and paracrine molecular developmental mechanisms which regulate branching morphogenesis in the mouse embryo lung, will provide fundamental insights into epithelial-mesenchymal interaction, and may lead to novel preventive and therapeutic strategies for lung immaturity, lung injury and lung repair.